AVO 8 MkIII Restoration
This AVO was previously owned by the FCO (Foreign Office) with a reference number of 00768.
FCO was a ministerial department from October 1968 to September 2020. The AVO 8 MKIII is probably dated around the 1968 time though there are no dates anywhere on the internals.
I found a price list published by AVO in 1968 which had the 8MKIII at £23&10shillings, which accounting for inflation would be £340 at today’s prices.
Initial state.
FCO was a ministerial department from October 1968 to September 2020. The AVO 8 MKIII is probably dated around the 1968 time though there are no dates anywhere on the internals.
I found a price list published by AVO in 1968 which had the 8MKIII at £23&10shillings, which accounting for inflation would be £340 at today’s prices.
Initial state.
Very dirty and the front glass has been pushed in, onto the meter movement. This is a common issue as the glass is only held in by a glue seal and 4 brass lugs, when picking up the AVO it was too easy to grab it front to back with the fingers or thumb pressing in on the glass, particularly if the strap was 'not trusted'!
First job was to clean the case back and battery box, I tested various solvents on the Bakelite, including Water, Peroxide, Isopropanol, Acetone, Windex, WD40, MEK, none of which worked well, the most successful was UBIK2000, used to remove oxidation from conservatory plastics. The battery box was treated with White vinegar and fibre glass brushing. |
The movement itself tested OK, which was a relief but still needed dismantling to clean the dial face. I had to backtrack a bit on the solvents as I didn’t want to risk damaging the printing, the best solution was Windex (Windolene) as this removed the main muck but not the printing, I did test UBEK2000 on a small area... it restored the white area to pure white, but it also started to lift the print. |
I tested the meter on various ranges against a Fluke multimeter and were in general within spec, I don’t have the equipment to test much of the A.C. range or voltages above 100v but as the lower ranges were OK it would seem reasonable to assume the higher ones were too. I noticed that someone had been in previously and ‘adjusted’ some of the DC Voltage dropper resistors, perhaps it had been in somewhere for a better calibration. As this was always meant to be a 'minimal intervention' restoration I decided not to make any adjustments myself. A calibration lab would be better suited for this. In previous employment we would have normally marked the meter as 'indicator only' when any form of compliance standard was required, and the meter had not been ‘calibrated’.